IL-7Ralpha expression on CD4+ T lymphocytes decreases with HIV disease progression and inversely correlates with immune activation.

Many factors can influence the rate of HIV disease progression, including those that maintain T cell homeostasis. One key homeostatic regulator is the IL-7 receptor (IL-7R). Previous studies have shown IL-7R expression levels decrease in HIV infection, but effects on memory subtypes, CD4(+) T cells, and cell function have not been explored. The present study examined the expression of the IL-7Ralpha chain on naïve and memory T lymphocyte subsets of both HIV-positive and HIV-negative individuals from Nairobi, Kenya to assess the role of IL-7Ralpha in HIV disease. Expression of IL-7Ralpha was significantly reduced in all CD4(+) and CD8(+) T cell subsets in HIV-positive individuals. This reduction was further enhanced in those with advanced HIV progression. Expression of IL-7Ralpha was inversely correlated to immune activation, and apoptosis, and was positively correlated with CD4 count in both bivariate and multivariate analysis. Expression of IL-7Ralpha did not correlate with HIV viral loads, indicating the elevated immune activation seen in HIV-infected individuals may be impacting expression of IL-7Ralpha, independent of viral loads. Signaling via the IL-7R is essential for T cell homeostasis and maintenance of T cell memory. Reduction of this receptor may contribute to the homeostatic disruption seen in HIV.

CD4+ T cell responses in HIV-exposed seronegative women are qualitatively distinct from those in HIV-infected women.

The immune response of human immunodeficiency virus (HIV)-exposed seronegative (ESN) women may be qualitatively different from that in those infected with HIV (HIV(+)). In a cohort of female commercial sex workers in Nairobi, Kenya, we found significantly lower (P< or =.01) levels of CD4(+)-specific immune activation and apoptosis in the ESN women compared with those in the HIV(+) women. Compared with the HIV(+) women, a lower proportion of the ESN women showed p24 peptide pool responses by the short-term, CD4(+)-specific, interferon (IFN)- gamma intracellular cytokine staining assay, whereas the proportion showing responses by the long-term, CD8(+)-depleted T cell proliferation assay was similar. Interestingly, the ESN responders had a 4.5-fold stronger proliferation response (P=.002) than the HIV(+) group. These data suggest that, compared with those in HIV(+) women, CD4(+) T cells in ESN women have a much greater ability to proliferate in response to p24 peptides.

Elevation of immune activation in kenyan women is associated with alterations in immune function: implications for vaccine development.

The infectious burden leading to immune activation can vary between different populations and lead to various immune dysfunctions. We compared the effect of immune activation on apoptosis and T cell function in HIV uninfected individuals from Nairobi, Kenya (n=34), and Winnipeg, Canada (n=10). Women from Nairobi had a significantly greater number of CD8+ T cells expressing the activation markers CD38 and HLA DR. Kenyan women also had significantly higher levels of CTLA-4+ CD4 and CD8+ T cells, and reduced levels of CD28+ CD8+ cells. Levels of CD95+ CD4+ T cells were higher in Kenyan women and, correspondingly, showed higher levels of spontaneous apoptosis. Kenyan women also demonstrated hyper-responsiveness to T cell activation as assessed by interferon gamma production. This study demonstrates that in a population of Kenyan women with high levels of T cell activation, there were also elevated levels of T cell apoptotic death and hyper-responsiveness. These differences may influence the efficacy of immune responses to pathogens and must be considered when testing candidate vaccines.

Development of a novel allo-independent HIV-1 virus preparation for use in immunoassays.

The study of the immunologic response to whole human immunodeficiency virus type 1 (HIV-1) antigen is limited by the presence of highly immunogenic human leukocyte antigen (HLA) alloantigens on the envelope of wild type virus. This paper outlines the production of HIV-1 infectious virions free of HLA for use as whole viral antigens in immunoassays. An infectious molecular clone of HIV-1 was transfected into the K-562 cell line, which does not express HLA on the cell surface. After a 30-day selection period, to ensure stable transfection, cells and culture supernatants were analyzed for productive HIV-1 infection and virion infectivity. An enzyme-linked immunosorbent assay (ELISA) confirmed the presence of p24 in the culture supernatants. Molecular confirmation of HIV-1 transfection was achieved by gene amplification. Flow cytometric analysis was used to identify gp120 on the surface of the infected cells. Viral supernatants were tested for HIV infectivity in peripheral blood mononuclear cells (PBMCs). The usefulness of this viral preparation as whole virus antigens was validated using PBMCs from HIV-infected individuals. These results indicate the successful production of HIV-1 infectious virions, which do not have HLA molecules on their viral envelope, and demonstrate their utility for immunoassays.